1. Technical Field of the Invention
The present invention relates to a sound field control device that imparts a sound field effect to an audio signal to control a sound field, and more particularly to sound field effect control according to a reproduction environment where the audio signal is reproduced.
2. Description of the Related Art
A conventional sound field control device imparts a sound field effect to sound of audio contents and controls the sound field (for example, see Japanese Patent No. 2755208). The sound field effect is an effect for reproducing sounds simulating reflected sounds generated in an acoustic space such as a concert hall to allow the listener to experience a sense of presence or reality such that the listener feels as though they were located in a different space such as a real concert hall while they are actually located in a room.
FIGS. 1(A) to 1(C) are conceptual diagrams illustrating a conventional process for localizing a virtual sound source. Specifically, FIG. 1(A) illustrates arrangement of speakers connected to a sound field control device, FIG. 1(B) illustrates an image of distribution of sound sources of direct and reflected sounds, when sounds to which a sound field effect has been imparted have been reproduced, and FIG. 1(C) is a graph illustrating an echo pattern of a hall (specifically, a graph representing the generation times and levels of direct and reflected sounds).
In the conventional sound field control device, volumes of sounds reproduced from speakers SP1 to SP5 arranged in a room H as shown in FIG. 1(A) are previously adjusted during setting or the like such that the volumes of the sounds are equal at a sound receiving point (listening position) J.
When the sound field control device is set so as to impart a sound field effect simulating a sound field of a hall, the sound field control device emits a sound as a direct sound through each speaker after or without performing a specific process on an input signal (i.e., a signal of a sound included in the content) as shown in FIG. 1(B). The sound field control device generates signals of sounds (sound field effect sounds), which simulate a plurality of reflected sounds, from the input signal based on sound field effect information of the hall, and emits the plurality of reflected sounds through the speakers as shown in FIG. 1(B). Here, the generation times and levels of the direct sound and the plurality of reflected sounds (sound field effect sounds) have, for example, a relationship as shown in FIG. 1(C).
The sound field effect information is information for reproducing sound field effect sounds. The sound field effect information includes impulse response characteristics of a group of reflected sounds generated in an acoustic space such as a concert hall or position information of respective virtual sound sources of the group of reflected sounds. In the following description, each reflected sound in an acoustic space such as a concert hall that the sound field control device generates from an input signal is referred to as a “sound field effect sound” as described above and is distinguished from each reflected sound generated through reflection of the sound from the walls of a listening room.
The conventional sound field control device has a problem in that an intended sound field effect is not obtained due to a difference in a real reproduction environment such as a difference in the direction or the arrangement of speakers within a room.
Such a difference in the sound field effect due to a difference in the reproduction environment is caused not only by a difference in the distance between the speakers and the sound receiving point but also by a difference in the size, material (or reflectivity), or the like of the room.
If the sound field effect is too strong, the sound field effect interferes with listening since the sound field effect sounds harsh. On the other hand, if the sound field effect is too weak, the practical value of the sound field effect function is reduced since it is hard to hear the sound field effect sound.